The present invention relates generally to an apparatus and method for the fumigation and detoxification of plant seed such as rice, corn, cottonseed, soybeans, peanuts, wheat, barley and other seeds. More particularly, the present invention relates to a pneumatic apparatus having a positive pressure air source, seed feed, a vacuum wheel air lock, fumigant and detoxicant source, a spraying apparatus for introducing the fumigant and/or the detoxicant and an exit cyclone having an optional air return for returning fumigant/detoxicant saturated air to the apparatus. Further, the inventive apparatus and method have been found effective for aflatoxin B.sub.1 and B.sub.2 suppression as well as for extermination of pink boll worm and weevils which commonly infest and contaminate the nation's seed supply and food chain. In addition to the efficacious fumigant and detoxicant activity of the present invention, increases in nutrient values of the treated seeds has been noted.
At present time conventional means for fumigation and detoxication of the nation's seed supply has been accomplished by employing the highly toxic chemicals phostoxin and methyl bromide. Despite their inherent toxicity these two chemicals are the major fumigants and detoxicants currently employed by growers and/or seed treatment facilities to comport with the U.S. Department of Agricultural (hereinafter "USDA") regulations and requirements for qualification for the Phyto-Sanitary Certificate of Approved Fumigation which is required for interstate transport of treated seed.
Current methodology and regulation mandates, for example, that cotton planting seed stored for interstate transport must be covered, treated and retained in such state for at least five days before transportation from the storage area. The five day retention period has been found to be the optimum time permissible for insuring safe levels of residual phostoxin or methyl bromide toxicity. This retention period had been tremendously burdensome to cotton gins which do not have endless seed storage capacity and must, at times, abandon or ignore proper storage procedures.
Planting and feed seed growers have, accordingly, suffered significant loss of revenue due to the regulatory storage period to insure safe levels of phostoxin and methyl bromide toxicity levels upon interstate transport of the seed. It has been found desirable, therefore, to eliminate these commonly employed toxic chemicals, as the major fumigants and detoxicants for seed treatment. Moreover, it has been determined that by employing alternative fumigants and detoxicants having less toxicity, the requisite seed retention period may be reduced from five days to a period of forty-eight to seventy-two hours. This reduced storage period results in far quicker turnaround times for the seed growers as well as the seed transporters in interstate commerce.
In accordance apparatus and method of fumigation and detoxification of seeds, the present invention has been found to achieve a more complete effective coating of each seed with a concomitant increase in fumigant and detoxicant activity. It well known that ammonia, in various forms, exhibits aflatoxin suppression activity in cottonseed at ambient temperature and pressure. See, e.g., Jorgensen, K. V., et al, "Atmospheric Pressure-Ambient Temperature Reduction of Aflatoxin B.sub.1 in Ammoniated Cottonseed," J. Agric. Food Chem., Vol 29, No. 3, p. 555; Price, R. L., et al, "Ammoniation of Whole Cottonseed at Atmospheric Pressure and Ambient Temperature to Reduce Aflatoxin M.sub.1 in Milk," J. Food Protection, Vol. 45, March, 1982, p. 341; and U.S. Pat. No. 3,429,709 issued Feb. 25, 1969 to Masri, et al. entitled "Process for De-Toxifying Substances Contaminated with Aflatoxin". Heretofore, however, it has been found exceedingly difficult to employ anhydrous ammonia in a detoxification system operating at ambient temperature and pressure. The principal problem encountered with ammoniation treatment to detoxify aflatoxin contaminated seed has been pH control. It is well known that an overly alkaline or overly acidic pH will rapidly degrade the nutrient value of the seed or kill it altogether. Furthermore, an overly alkaline pH causes alkaline hydrolysis which causes rapid decomposition of fumigants or pesticides commonly applied prior to, concurrently with, or shortly after treatment with the ammonia detoxicant. As a result of this difficulty in pH control, there has been an inability on the part of those skilled in the art to develop an apparatus and method of detoxification and fumigation which effectively reduces the seed storage time and significantly increases fumigant activity and duration.
Apart from aflatoxin suppression, a principal concern to seed producers is insect damage during storage. Frequently, large amounts of seed will be stored for periods up to a year, during which time, the vast majority of the seed is exposed to insect infestation and damage. The annual monetary losses resulting from insect damage have, for a considerable time, been substantial and continue to mount. Accordingly, seed producers have sought, for a long period of time, an effective fumigant having a long lasting fumigant activity to protect the seed from insect infestation during its period of storage. Currently, the majority of seed producers are employing the toxic, though USDA approved, chemicals phostoxin and methyl bromide to control insect infestation in stored seed. However, these chemicals are highly toxic and exceedingly dangerous to handle.
It is well known, to those skilled in the art, that organic pyrethrins exhibit potent fumigant activity and protect seeds and grains from insect damage while exhibiting lower toxicity to humans than phostoxin and methyl bromide. Organic pyrethrin has been mixed with piperonyl butoxide, a synergist, in both water and oil based emulsions to achieve a protective biocidal activity for up to one year when applied to various grains and fruits. See, e.g., Dove, W. E. et al, "Protection of Stored Grain with Sprays of Pyrethrins-Piperonyl Butoxide Emulstion," Agric. and Food Chem, Vol. 3, No. 11, November 1955 pp. pp 932-936; Dove, W. E., "Piperonyl Butoxide and Pyrethrins for the Protection of Grains and Similar Products from Insect Damage," Trans. Ninth Int. Congr. Ent., Vol. 1, 1952, pp. 875-879; Amos, T. G., et al., "Laboratory Evaluation of Pyrethrins for use on Processed Sultanas as a Protectant against Insect Infestation," Pyrethrum Post, Vol. 14, No. 3, pp. 72-75; and Amos, T. G., et al., "Use of Synergised Pyrethrins to Protect Processed Sultanas from Insect Attack," Pyrethrum Post, Vol. 14, No. 3, pp. 76-78.
Heretofore, however, it has been found exceedingly difficult to employ a pyrethrin/piperonyl butoxide fumigant in high volume commercial applications. The primary difficulties encountered in translating laboratory data to commercial application of organic pyrethrins as a fumigant for stored grain, have been pH control, a high susceptibility to alkaline hydrolysis and instability in air and sunlight.